The domain within your query sequence starts at position 188 and ends at position 232; the E-value for the RING domain shown below is 3.17e0.

CEVCGRSDREDRLLLCDGCDAGYHMECLDPPLQEVPVDEWFCPEC

RING

Ring finger

SMART accession number:

SM00184

Description:

E3 ubiquitin-protein ligase activity is intrinsic to the RING domain of c-Cbl and is likely to be a general function of this domain; Various RING fingers exhibit binding activity towards E2 ubiquitin-conjugating enzymes (Ubc' s)

Zinc finger (Znf) domains are relatively small protein motifs which contain multiple finger-like protrusions that make tandem contacts with their target molecule. Some of these domains bind zinc, but many do not; instead binding other metals such as iron, or no metal at all. For example, some family members form salt bridges to stabilise the finger-like folds. They were first identified as a DNA-binding motif in transcription factor TFIIIA from Xenopus laevis (African clawed frog), however they are now recognised to bind DNA, RNA, protein and/or lipid substrates [(PUBMED:10529348), (PUBMED:15963892), (PUBMED:15718139), (PUBMED:17210253), (PUBMED:12665246)]. Their binding properties depend on the amino acid sequence of the finger domains and of the linker between fingers, as well as on the higher-order structures and the number of fingers. Znf domains are often found in clusters, where fingers can have different binding specificities. There are many superfamilies of Znf motifs, varying in both sequence and structure. They display considerable versatility in binding modes, even between members of the same class (e.g. some bind DNA, others protein), suggesting that Znf motifs are stable scaffolds that have evolved specialised functions. For example, Znf-containing proteins function in gene transcription, translation, mRNA trafficking, cytoskeleton organisation, epithelial development, cell adhesion, protein folding, chromatin remodelling and zinc sensing, to name but a few [(PUBMED:11179890)]. Zinc-binding motifs are stable structures, and they rarely undergo conformational changes upon binding their target.

This entry represents RING-type zinc finger domains. The RING-finger is a specialised type of Zn-finger of 40 to 60 residues that binds two atoms of zinc, and is probably involved in mediating protein-protein interactions [(PUBMED:8317827), (PUBMED:8804826), (PUBMED:8744354)]. There are two different variants, the C3HC4-type and a C3H2C3-type, which are clearly related despite the different cysteine/histidine pattern. The latter type is sometimes referred to as 'RING-H2 finger'. The RING domain is a protein interaction domain that has been implicated in a range of diverse biological processes. E3 ubiquitin-protein ligase activity is intrinsic to the RING domain of c-Cbl and is likely to be a general function of this domain. E3 ubiquitin-protein ligases determine the substrate specificity for ubiquitylation and have been classified into HECT and RING-finger families. More recently, however, U-box proteins, which contain a domain (the U box) of about 70 amino acids that is conserved from yeast to humans, have been identified as a new type of E3 [(PUBMED:12944364)]. Various RING fingers also exhibit binding to E2 ubiquitin-conjugating enzymes (Ubc's) [(PUBMED:10662664), (PUBMED:10514377), (PUBMED:10577187)].

Several 3D-structures for RING-fingers are known [(PUBMED:8804826), (PUBMED:8744354)]. The 3D structure of the zinc ligation system is unique to the RING domain and is referred to as the 'cross-brace' motif. The spacing of the cysteines in such a domain is C-x(2)-C-x(9 to 39)-C-x(1 to 3)-H-x(2 to 3)-C-x(2)-C-x(4 to 48)-C-x(2)-C. Metal ligand pairs one and three co-ordinate to bind one zinc ion, whilst pairs two and four bind the second.

Note that in the older literature, some RING-fingers are denoted as LIM-domains. The LIM-domain Zn-finger is a fundamentally different family, albeit with similar Cys-spacing (see IPR001781).

Ubiquitination targets proteins for degradation and is a potent regulator of cellular protein function. Recent results implicate the RING finger domain in specific ubiquitination events; it is possible that all RING proteins act as E3 ubiquitin protein ligases, with implications for a variety of biological areas.

Ubiquitination of receptor protein-tyrosine kinases (RPTKs) terminates signaling by marking active receptors for degradation. c-Cbl, an adapter protein for RPTKs, positively regulates RPTK ubiquitination in a manner dependent on its variant SRC homology 2 (SH2) and RING finger domains. Ubiquitin-protein ligases (or E3s) are the components of ubiquitination pathways that recognize target substrates and promote their ligation to ubiquitin. The c-Cbl protein acted as an E3 that can recognize tyrosine-phosphorylated substrates, such as the activated platelet-derived growth factor receptor, through its SH2 domain and that recruits and allosterically activates an E2 ubiquitin-conjugating enzyme through its RING domain. These results reveal an SH2-containing protein that functions as a ubiquitin-protein ligase and thus provide a distinct mechanism for substrate targeting in the ubiquitin system.

This information is based on mapping of SMART genomic protein database to KEGG orthologous groups. Percentage points are related to the number of proteins with RING domain which could be assigned to a KEGG orthologous group, and not all proteins containing RING domain. Please note that proteins can be included in multiple pathways, ie. the numbers above will not always add up to 100%.